In this paper, we present a novel smart home system integrating energy efficiency features. The smart home application is built on top of Hydra, a middleware framework that facilitates the intelligent communication of heterogeneous embedded devices through an overlay P2P network. We interconnect common devices available in private households and integrate wireless power metering plugs to gain access to energy consumption data. These data are used for monitoring and analyzing consumed energy on device level in near real-time. Further, transparent information about the energy usage can be used to efficiently program and control home appliances depending on various factors, e.g. the electricity price. Making more and more data available to end-users, brings with it further challenges in the area of user interfaces. Hence, we complete the smart home system by intuitive user interfaces presenting energy consumption data in meaningful contexts and allowing end users to interact with their environment. We argue, that the combination of both, a technically sophisticated smart home application and at the same time transparent, intuitive user interfaces showing information regarding the energy usage, e.g. energy price, energy source, standby consumption etc., has the potential to bring the vision of the energy efficient smart home within reach.